proc bgsleep {delay} {
   set final_time [expr ([clock seconds] * 1.0) + (($delay * 1.0) / 1000.0)]

   set activation_var [join [list BGSLEEP WAIT FOR $final_time [expr rand()]] _]
   global $activation_var

   after $delay [list set $activation_var 1]
   vwait $activation_var
 }